Nitrogen and potassium nutrition affect yield, dry weight partitioning, and nutrient-use efficiency of sweet potato

The effects of nitrogen (N) and potassium (K) nutrition on yield, dry weight partitioning, and N- and K-use efficiency of three sweet potato [Ipomoea batatas L. (Lam.)] cultivars (Centennial, Regal, and Jewel) were investigated in field and container studies. Differences in yield among cultivars depended on the N and K rates. Overall, Regal was the highest yielding cultivar. Yield of Regal was higher than Jewel at most of the N×K rate combinations, and higher than Centennial at one N×K rate combination. There were no significant differences in yield between Centennial and Jewel. Significant cultivar×nutrient interactions were found for dry weight expressed on a per plant basis, but interactions were not significant when expressed as % of the total dry weight. Jewel was the most efficient in terms of dry weight partitioning to the storage roots (67%), followed by Regal (64%) and Centennial (62%). Centennial had significantly higher K-use efficiency in comparison to Jewel or Regal. Cultivars did not differ significantly in N use efficiency. Dry weight partitioning to the storage roots, and N- and K-use efficiency decreased with each increment in the N rate. With each increment in the K rate, dry weight partitioning to the storage roots and N use efficiency increased, while K-use efficiency decreased. Yield, dry weight partitioning, or nutrient-use efficiency can be increased by manipulating nitrogen and potassium nutrition. The variability among cultivars in K-use efficiency and dry matter partitioning suggest that the development of cultivars with improved nutrient utilization is possible.